Closer Grant Balfour is ready for the celebration to begin after striking out the side in the ninth inning.

Photo: Lance Iversen, The Chronicle

Closer Grant Balfour is ready for the celebration to begin after...

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Dylan Collier of Richmond, reacts as the final out is called and the A's clinched a playoff spot for the first time in six years. The Oakland Athletics clinched a playoff spot on Monday, October 1, 2012, after they defeated the Texas Rangers at O.co Coliseum in Oakland, Calif.

Photo: Carlos Avila Gonzalez, The Chronicle

Dylan Collier of Richmond, reacts as the final out is called and...

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Oakland Athletics Coco Crisp back to camera is strayed with Champaign in the A's club house after they beat the Texas Rangers 4-3 Monday October 1, 2012 in Oakland California

Photo: Lance Iversen, The Chronicle

Oakland Athletics Coco Crisp back to camera is strayed with...

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Members of the Oakland Athletics celebrate their 4-3 win over the Texas Rangers Monday October 1, 2012 in Oakland California

Photo: Lance Iversen, The Chronicle

Members of the Oakland Athletics celebrate their 4-3 win over the...

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OAKLAND, CA - OCTOBER 01: The Oakland Athletics celebrates after the Athletics beat the Texas Rangers to clinch a playoff spot at O.co Coliseum on October 1, 2012 in Oakland, California. (Photo by Ezra Shaw/Getty Images)

The A's aren't the only ones who believe. The Rangers believe in them, too.

"Nobody thought they'd be where they are, but I'm never surprised with what happens over there in the clubhouse of the Oakland A's," Texas manager Ron Washington said. "They've always got pitching."

And this year, they've got hitting. And defending. And baserunning.

Not to mention celebrating.

Oh, this team knows how to celebrate. Even without the benefit of one of its familiar walk-off victories.

For the first time in six years, the A's are going to the playoffs. The American League West was supposed to feature a two-team race between the Rangers and Angels, but the A's shocked the division and the league, along with all the experts.

After closer Grant Balfour struck out the side in the ninth inning Monday night, saving a 4-3 victory over the Rangers, he leaped into the arms of catcher Derek Norris, and a sea of green and gold poured onto the field for a mob-fest that seemed so unlikely when this group gathered for spring training eight months ago.

The A's clinched a wild-card spot. Two more wins over the Rangers, and they would clinch a division title.

For a team that didn't appear too potent in March, the A's sure seem potent in October. For a team that supposedly wasn't built to contend in the regular season, the A's sure are built nicely for the postseason.

"One hundred percent," Jonny Gomes said through the mist of Champagne and the cigar smoke. "Pitching, defense and the long ball. That's recession-proof right there. Once you get in, it's no longer the best team. It's who's hot."

"If you look at their numbers, that's one thing where numbers don't come into play: .215, .218, .230. Yeah, but make a mistake to them," said Washington, making a dare. "They've got guys over there sitting on the bench with 14, 15 home runs.

"They swapped their shortstop out. They swapped their second baseman out. They swapped their first baseman out. And they continue to roll, man, because they believe."

I asked Washington, the manager of the two-time defending AL champions and a former A's coach, if the A's will be a dangerous playoff team.

"I don't know," he said. "I think that would have to depend on how they react to being in the postseason. If they react like they're reacting now - like, who cares? - then they could be."

Washington wasn't accusing the A's of being apathetic but complimenting them for being loosey-goosey at a time most young teams would be tight.

And darned good.

"We have a great bullpen and the ability to change the score with one swing," said Brandon Moss, whose one swing in the fifth inning gave the A's their deciding run. It was a shallow sacrifice fly to center, scoring Coco Crisp. Actually, Moss was referring to Oakland's home run pop.

"That's like the Yankees. That's what they do. Look at the Tigers. That's what they do. A lot of postseason teams, that's what they do."

The Rangers and Angels were supposed to be the big power threats, but the A's have the most homers in the majors since the All-Star break, 110. They took a break from the long ball Monday and showed off other elements for which they're known.

Starter Jarrod Parker pitched into the seventh inning, and three relievers - Sean Doolittle, Ryan Cook and Balfour - retired nine straight batters. The A's put together two-run rallies in the first and fifth innings, and that was enough.

The A's have made a tradition of delivering an on-field pie in the face of the guy responsible for a game-ending RBI. On Monday, manager Bob Melvin was targeted, and he loved every minute of it.

"Bob's always been a good manager," Washington said. "To take that group where they are right now, wow, you've got to admire him. They play like they belong."

Washington endorsed Melvin for AL Manager of the Year over Baltimore's Buck Showalter - "I only say that because Buck had a lot more to work with than Bob had to work with other than the pitching. Bob had better pitching, but Buck found a way. ... You've got to give Buck credit."

On Monday, it was all about the A's, who play the Rangers twice more for the division title, hoping for one more celebration before beginning their improbable playoff journey.